If you will be painting on a model with UVs in Mudbox, consider the following items before exporting the model from your 3D modeling application. The first three requirements are the most critical.
| Requirement | Criteria |
|---|---|
| UV texture coordinates |
UVs are a coordinate system that let you apply 2D images to 3D surfaces by correlating the pixels you paint on an image to where they appear on the model. A model must have UV texture coordinates (UVs) to be painted in Mudbox. For more information, see UVs overview. You can quickly tell if a model has UVs after loading it into Mudbox by clicking the UV View tab to display the UV View. If the model has UVs you see a mesh that appears similar to the 3D version of the model but flattened as a 2D representation. The UVs may also appear in several pieces depending on how they were laid out in the original 3D modeling or UV editing application. Note:
If your model does not contain UV texture coordinates you will need to create and arrange them using a 3D modeling or UV editing application equipped with UV creation and editing tools. Maya and 3ds Max have tools for this purpose. The tips described in this topic can help you arrange the UVs in those applications for use within Mudbox. In general, you want the UV editing on your 3D model to be finalized before you begin your 3D painting in Mudbox. Otherwise, the UVs can become misaligned with your paint work. If UVs do change during production, you can transfer your paint layers to an updated mesh. See Transfer paint layers. |
| Overlapping UVs |
UVs need to be laid out in your 3D modelling or UV editing application so they are contained within the UV tile region and do not lie partially across a UV tile border. Lay UVs out in your 3D modeling or UV editing application so they do not overlap, unless you want to take advantage of the model’s symmetry or reuse a portion of the image that is repeated on the model to save texture space. For example, overlapping UVs are useful when you paint an image on one half of a symmetrical model and reuse it on the opposite half. You can also reuse the same area on a texture map for visual elements that are repeated such as windows or brickwork on a building, wheels on a car, fingers on a hand, and so on. Many 3D applications provide a feature for visually confirming overlapping UVs. If UVs are unintentionally partially overlapped, you may get unexpected results when painting. |
| Painting artifacts when using automatic UV generation | If you see painting artifacts when using UVs auto-generated from a mesh, try temporarily increasing Tile Count and decreasing the Bleed value in the preferences before recreating the UVs. Alternatively, export the mesh to a program such as Maya or 3ds Max and generate UVs there. |
| Spacing around UV shells |
The UVs need to be laid out with a 4-6 pixel wide empty region along the outside perimeter of each UV shell to account for the automatic edge bleed that occurs when painting. If the UVs are spaced too close to each other, or are positioned too close to the edge of image borders (UV tile edge) seams and paint artifacts can appear on the model when painted. |
| Shape and relative size of UV faces in relation to the 3D faces |
Whenever possible, the shape and relative size of the UV faces should roughly correlate to each other and to the shape of the corresponding polygonal faces on the model. This way, the number of pixels allotted to represent the detail on a particular UV shell is roughly consistent from face to face. Otherwise, when a large polygonal face occupies a very small space on the image (UV tile) it appears soft by comparison to a similarly sized polygonal face occupying a larger space on the image, because its detail is represented by fewer pixels in the image. In some situations, you may want to scale particular UV shells larger in relation to others within the image area (UV tile) to achieve more visual detail. For example, the face of a recognizable character, a detailed console on a spacecraft, or a company logo can require those UVs to be scaled larger so they occupy a larger area on the UV tile and produce the highest texture quality possible in the rendered image. |
| Maximize the area occupied by the UVs |
UVs need to fill the image area (UV tile) as much as possible. This maximizes the resolution provided by the image you paint. This often requires that you rotate the UV shells to fit into a particular location (much like a tailor rotates pieces of a pattern template on top of a piece of cloth). You can also try to minimize the number of unnecessary breaks between the UV shells to help reduce the number of elements that have to fit in the image area (UV tile). This also maximizes pixel space on the image and helps to reduce the potential for the appearance of seams. These criteria must be balanced with the criteria described earlier in this topic. For example, when two adjacent UV faces are also adjacent to each other in the UV layout, but are disconnected, they might be more easily sewn together in your 3D modeling or UV editing application prior to the model being painted in Mudbox. This can minimize the possibility of a seam appearing on the model and ensure that the image you paint takes full advantage of the resolution you specify in the paint layer. |